Lightning Electromagnetics

Robert Gardner

• Publisher: CRC Press
• Year: 2017
• Print ISBN: 9780891169888
• eBook ISBN: 9781351435376
• Topic: Technology & Engineering
• Subtopic: Electrical Engineering & Telecommunications
• Index: Technology & Engineering

A survey of theoretical and experimental research, this book covers all areas of lightning phenomenology. The four sections cover models of fundamental lightning processes, propagation of lightning-induced signals, measurement of lightning parameters, and lightning interaction with systems. The book provides an excellent review of the use of models to support remote sensing efforts. It includes data on high-frequency radiated fields for lightening and an overview of the data available in the frequency and time domains for lightning. The book also presents spectoral and temporal characteristics of lightning in the VHF-UHF frequency range and uses photographic and electromagnetic measurements to examine how lighting chooses a strike point.

PART A:

MODELS OF FUNDAMENTAL LIGHTNING PROCESSES

PROPERTIES OF LIGHTNING-LEADER PULSES

C. E. Baum, Air Force Weapons Laboratory, Kirtland AFB, New Mexico 87117, USA

ABSTRACT

Recent measurements have shown that lightning leader pulses have very fast rise times. Characteristic times for the rise of as small as a little less than 30 ns have been observed. Considering the nature of these leader pulses, an approximate model is obtained. This model is based on an equivalent transmission line as sometimes used in antenna theory. A corona which increases the capacitance per unit length is assumed to form around the central arc channel. Letting the corona radius be governed by a simple breakdown model, a nonlinear wave equation is obtained for the arc. Solving this equation one obtains velocities of the order of 10⁸ m/s and currents of the order of 15 kA; this agrees well with the data.

1. INTRODUCTION

Recent measurements have shown that lightning pulses can have very fast characteristic times in their rises. For leader-like pulses this can be less than 30 ns with typical times somewhat longer (Baum, 1980a). For return-stroke-like pulses, this can be less than 50 ns with typical times somewhat longer (Baum, 1980a; Weidman and Krider, 1980).

For the leader pulses, the electromagnetic field data could be extrapolated back to the source to give sources (time derivative of the volume integral of current density) consistent with tens of kA and velocities of the order of 10⁸ m/s (Baum, 1980a). Since these pulses have obvious importance for lightning interaction with electronic systems, one would like to have one or more models to explain their behavior, so as to have an eventual quantitative understanding in the usual senses. This note develops a very approximate nonlinear transmission-line model of the lightning leader propagating through previously undisturbed air (or under similar conditions). Some of these points have been covered in a spoken paper (Baum, 1981).

2. EQUIVALENT CORONA RADIUS

The concept of an equival...

Table of contents

• Cover
• Half Title
• Title Page
• Copyright Page
• Table of Contents
• Preface
• PART A: MODELS OF FUNDAMENTAL LIGHTNING PROCESSES
• PART B: PROPAGATION OF LIGHTNING-INDUCED SIGNALS
• PART C: MEASUREMENT OF LIGHTNING PARAMETERS
• PART D: LIGHTNING INTERACTION WITH SYSTEMS
• Index